Production stimulation method for oil wells



United States Patent 3,386,511 PRODUCTION STIMULATION METHOD FOR OIL WELLS Frank J. Messina, 440 Granada Drive, La Habra, Calif. 90631 No Drawing. Filed June 27, 1966, Ser. No. 560,793 9 Claims. (Cl. 16638) In the production of oil, there are many localities in which oil bearing formations are found, but from which it is extremely diflicult to produce oil due to the tightly packed nature of the formation, the heavy viscosity of the oil, or a combination of both.

A variety of techniques have been developed and used to a limited extent in the past in an endeavor to make oil bearing formations more porous and thus permit passage of a freer flow of oil-containing fluids therethrough, as well as heating the oil bearing formation by steam, or the like, to decrease the viscosity of the oil or oil-containing fluids therein.

Such prior methods and techniques have met with limited success, due primarily to the high cost involved in heating the formations relative to the increased revenue obtained from increased oil production. Also, heating of such formations in the past has been done by the use of open flames or electrical resistance elements, whereby unduly high temperatures have been attained which resulted in charring of oil in the formations, which decreased rather than increased the rate of fluid flow from the formation to the well.

A major object of the invention is to provide a simple, inexpensive method of treating earth formations from which oil is produced to increase the porosity thereof and concurrently heat the formations so that oil therein or which thereafter flows therethrough will be of decreased viscosity, all to the end that the rate of oil-containing fluid to the well willbe increased.

Another object of the invention is to provide a method of treating an oil well requiring no elaborate or expensive equipment for the performance thereof, but in which common, commercially available materials are utilized.

A still further object of the invention is to supply a method of treating an oil well which may be carried out without the use of highly skilled personnel, and one that can be performed during the time a well is shut down for a relatively short period of time.

These and other objects and advantages of the invention will become apparent from the following description thereof.

The structure of a conventional oil well is known to those skilled in the art of oil production, and a drawing of a well relative to the present invention is not deemed necessary herein. Such an oil well includes a bore hole that extends underground to an oil bearing formation. A surface string of casing may be provided in the well, with additional strings of casing of smaller diameter depending therefrom that are cemented together to prevent entry of surface water into the bore hole as well as preventing contamination of surface water by oil or gas.

A tubing string extends downwardly through the oil well casing, and supports a pump on the lower end thereof that is actuated by a sucker rod. The tubing is supported by flanges, or the like, provided on the upper end of the surface string, which flanges can be removed when required to permit access to the interior of the casing and the oil producing formation. Normally, various valve means will be provided on the upper end of the tubing to regulate fluid flow therefrom. Also, valve means are usually provided on the flanges, which when open, establish communication between the annulus-shaped space existing between the casing and tubing and the ambient atmosphere. Thus, the flanges, as well as the valve previously mentioned, provide means of access to the interior of the casing and the oil producing formation.

In performance of the method of the present invention, it is preferable to remove the pump from the well. A first material, preferably a solid or liquid carbon dioxide, is discharged into the well by opening the flange or valve means connected to the upper end of the surface string of casing. The carbon dioxide falls to the bottom of the well due to the force of gravity, and is subsequently transformed into gaseous carbon dioxide when the solid or liquid form thereof is heated, which gas is substantially heavier than air.

A suflicient quantity of liquid or solid carbon dioxide is discharged into the well that when it transforms into the gaseous state, air in the well is discharged upwardly into the ambient atmosphere through the fiange or valve means which is in an open condition. In this manner the well is filled with a column of gaseous carbon dioxide, for reasons which will hereinafter become apparent. Preferably, the solid or liquid carbon dioxide is added to the well in a quantity greater than that required to provide the previously mentioned column.

After the first material has been added to the well, a

quantity of a second material is dropped thereinto, which.

latter material may be in the form of scrap aluminum, magnesium or zinc, or a suitable ore thereof, such as cryolite, which is a sodium aluminum fluoride.

Following the addition of a second material to the well, an aqueous solution of sodium hydroxide is discharged into the well, which when it comes into contact with the second material at the bottom of the well, causes an exothermic reaction resulting in the evolution of hydrogen gas. The flange or valve means previously mentioned are closed after the sodium hydroxide solution is added to the well.

From experience it has been found desirable to discharge a fourth material into the well concurrently with the sodium hydroxide solution, for this fourth material is one that tends to cause the exothermic reaction to at a substantially uniform rate. In practicing the present method, sodium glutomate has been used for the fourth material. which is preferably dissolved in the aqueous sodium hydroxide solution.

As the exothermic reaction occurs, the solid or 'liquid' carbon dioxide is transformed into the gaseous carbon dioxide, together with the hydrogen evolved from the reaction subjecting the oil producing formation in the earth to a substantial pressure. Concurrently, the oil producing formation is heated, with the heat and pressure cooperatively increasing the fluid-carrying capacity thereof by fracturing the same to form channels therein. Initially, the pressure on the inside of the well tends to force oilcontaining fluid in the formation away from the well.

After the formation is heated and the outwardly directed pressure on the formation subsides, the oil-containing fluid initially in the formation is forced backwardly therethrough towards the well. This backward flow of fluid towards the well takes place at a greater rate than that which prevailed before treatment of the well, for the formation is e not only more porous, but is heated, which heat reduces the viscosity of the oil-containing liquid. The backward flow of the oil-containing liquid is due to the force .to which the fluid is subjected after being forced outwardly in the formation away from the well. This force arises from the weight of the earth above the formation.

After substantial completion of the exothermic reaction, the flange or valve means are opened, to permit the pressure in the upper portion of the well to equalize with that of the ambient atmosphere. The pump and sucker rods are then reinstalled in the well, and the well replaced in production at a substantially increased rate over that which prevailed prior to the above described treatment.

The quantities of the first, second and third materials used in the present method will vary from well to well, depending not only upon the depth of the Well, but the extent to which it is desired to heat the oil producing formation outwardly from the well. From experience it has been found that with a shallow well, substantially 2000 feet in depth, satisfactory results may be obtained by using 186 pounds of scrap aluminum as the second material, with 275 pounds of sodium hydroxide dissolved in 297 gallons of water as the third. Twenty pounds of sodium glutamate is preferably dissolved in the sodium hydroxide solution as the fourth material.

The pressure on the oil containing formation arises not only from the vaporization of the solid or liquid carbon dioxide and the evolved hydrogen, but water arising from the reaction, coupled with water added to the well with the sodium hydroxide is converted to steam. The greater the quantity of soild or liquid carbon dioxide used in the treatment just described, the greater will be the quantities of the second and third materials required, for heat must be supplied to transform the solid or liquid carbon dioxide into a gas. Heat used in so transforming the liquid or solid carbon dioxide into a gas, is not available for heating the oil containing formation.

When the carbon dioxide is in the gaseous form it cooperates -with the evolved hydrogen and steam to provide an atmosphere in the well that will not support combustion, whereby no matter how high the temperature in the well and oil producing formation, there will be no charring of the oil to lessen the porosity of the formation.

Although the present invention is fully capable of achieving the objects and providing the advantages hereinbefore mentioned, it is to be understood that it is merely illustrative of :the presently preferred embodiment thereof and I do not mean to be limited to the details of construction herein described, other than as defined in the appended claims.

I claim:

1. The method of treating an oil well in which at least one string of casing is suspended therein, on the upper end of which means is provided that can be opened to permit access to the interior of said casing and the earth formation from which said well produces a fluid including oil, which means is capable of being closed to obstruct communication between the interior of said casing, said earth formation, and the ambient atmosphere, with said method comprising the steps of:

(a) opening said means and discharging a first solid or liquid material into said well, which upon being sub jected to heat, is transformed into an inert gas;

(b) discharging a second material into said well through said means after said first material has been discharged therethrough;

(c) discharging a third material into said well through said means after said second material has been discharged therethrough, with said third material being of such composition that when in contact with said second material an exothermic reaction develops with the evolution of a gas, which second and third materials are added to said Well in such quantitites as to transform all of said first material into a gas and heat in said formation, outwardly a substantial distance from said well;

(d) closing said means after said first, econd and third materials have been added to said well to permit said gas evolved from said exothermic reaction and said gas evolved from the transformation of said first material to increase the fluid-carrying capability of said formation when the pressure from said gases is exerted on said formation, with said fluid flowing into said well from said formation at a faster rate than before said treatment of said well due to heating of said fluid to lower the viscosity thereof and lend a greater fluid-carrying capability thereto; and

(e) opening said means to remove said fluid from said well after said formation has been subjected to said pressure and heat for a substantial period of time.

2. The method as defined in claim 1 which includes the further step of:

(f) purging substantially all of the air in said well by means of said inert gas resulting from the transformation of said first material.

3. The method as defined in claim 2 in which second material contains a substantial quantity of aluminum and said third material comprises an aqueous solution of a hydroxide of an alkaline earth.

4. The method as defined in claim 1 which includes the further step of:

(f) adding a fourth material to said well through said means, which fourth material cooperates with said second and third materials to control the evoluton of said exothermic reacton at a substantially uniform rate.

5. The method as defined in claim 1 in which said first material comprises either a liquid or solid carbon dioxide.

6. The method as defined in claim 1 in which said second material contains a metal that dissolves in said third material.

7. A method as defined in claim 1 which said second material contains a substantial quantity of aluminum.

8. The method as defined in claim 1 in which said second material includes one or more metals selected from a group thereof comprising zinc, magnesium and aluminum.

9. The method as defined in claim 3 in which said fourth material comprises sodium glutomate.

UNITED STATES PATENTS References Cited 2,811,209 10/1957 Elkins l6638 2,889,884 6/1959 Henderson et al 16638 2,975,834 3/1961 West et a1. 166-38 X 3,129,760 4/1964 Gambill 166--38 STEPHEN J. NOVOSAD, Primary Examiner. 

1. THE METHOD OF TREATING AN OIL WELL IN WHICH AT LEAST ONE STRING OF CASING IS SUSPENDED THEREIN, ON THE UPPER END OF WHICH MEANS IS PROVIDED THAT CAN BE OPENED TO PERMIT ACCESS TO THE INTERIOR OF SAID CASING AND THE EARTH FORMATION FROM WHICH SAID WELL PRODUCES A FLUID INCLUDING OIL, WHICH MEANS IS CAPABLE OF BEING CLOSED TO OBSTRUCT COMMUNICATION BETWEEN THE INTERIOR OF SAID CASING, SAID EARTH FORMATION, AND THE AMBIENT ATMOSPHERE, WITH SAID METHOD COMPRISING THE STEPS OF: (A) OPENING SAID MEANS AND DISCHARGING A FIRST SOLID OR LIQUID MATERIAL INTO SAID WELL, WHICH UPON BEING SUBJECTED TO HEAT, IS TRANSFORMED INTO AN INERT GAS; (B) DISCHARGING A SECOND MATERIAL INTO SAID WELL THROUGH SAID MEANS AFTER SAID FIRST MATERIAL HAS BEEN DISCHARGED THERETHROUGH; (C) DISCHARGING A THIRD MATERIAL INTO SAID WELL THROUGH SAID MEANS AFTER SAID SECOND MATERIAL HAS BEEN DISCHARGED THERETHROUGH, WITH SAID THIRD MATERIAL BEING OF SUCH COMPOSITION THAT WHEN IN CONTACT WITH SAID SECOND MATERIAL AN EXOTHERMIC REACTION DEVELOPS WITH THE EVOLUTION OF A GAS, WHICH SECOND AND THIRD MATERIALS ARE ADDED TO SAID WELL IN SUCH QUANTITIES AS TO TRANSFORM ALL OF SAID FIRST MATERIAL INTO A GAS AND HEAT IN SAID FORMATION, OUTWARDLY A SUBSTANTIAL DISTANCE FROM SAID WELL; (D) CLOSING SAID MEANS AFTER SAID FIRST, SECOND AND THIRD MATERIALS HAVE BEEN ADDED TO SAID WELL TO PERMIT SAID GAS EVOLVED FROM SAID EXOTHERMIC REACTION AND SAID GAS EVOLVED FROM THE TRANSFORMATION OF SAID FIRST MATERIAL TO INCREASE THE FLUID-CARRYING CAPABILITY OF SAID FORMATION WHEN THE PRESSURE FROM SAID GASES IS EXERTED ON SAID FORMATION, WITH SAID FLUID FLOWING INTO SAID WELL FROM SAID FORMATION AT A FASTER RATE THAN BEFORE SAID TREATMENT OF SAID WELL DUE TO HEATING OF SAID FLUID TO LOWER THE VISCOSITY THEREOF AND LEND A GREATET FLUID-CARRYING CAPABILITY THERETO; AND (E) OPENING SAID MEANS TO REMOVE SAID FLUID FROM SAID WELL AFTER SAID FORMATION HAS BEEN SUBJECTED TO SAID PRESSURE AND HEAT FOR A SUBSTANTIAL PERIOD OF TIME. 